Modern electronic devices, for example cellular phones, personal audio/video players, hand held video games, and global positioning systems, require a seamless integration of analog and digital subsystems. Furthermore, premiums are often placed on small size, complexity, and high performance. Thus, highly sensitive analog circuits frequently need to be placed very close to high-speed digital systems.
High-speed digital systems can switch at more than one billion times a second. At such switching speeds, switching currents tend to be high. Thus, such high-speed digital systems can radiate energy that interferes with highly sensitive analog circuits. Interference usually takes the form of signal crosstalk. While faraday shielding has been widely used to protect highly sensitive analog circuits from interference, the traditional faraday shields tend to be expensive in both space and labor content. Furthermore, their implementation must be undertaken with great foresight to determine where to install the shields, and with great care to actually protect the analog circuits. Moreover, the traditional faraday shield is not particularly flexible.
Traditionally, an integrated circuit is supplied as part of a semiconductor package having external leads for soldering, or otherwise connecting, to a printed circuit board. For example, surface mount leadless packages have been widely used with integrated circuit chips. In such packages, an integrated circuit chip is encapsulated in a ceramic or plastic housing having electrical leads that are suitable for soldering to a circuit board. Bonding conductors, which are also encapsulated in the housing, extend from the upper part of the electrical leads, which are within the package, to electrical pads on the integrated circuit chip.
A typical semiconductor package includes a lead frame, which is usually stamped out of a metal strip. The lead frame may include a plurality of leads held together by connectors that extend between the leads. The lead frame may further include a mounting pad.
Typically, the bond conductors are welded to the electrical leads and to the electrical pads. Next the lead frame, the integrated circuit chip, and the bonding conductors are then encapsulated. Finally the leads are cut and formed as required to complete the semiconductor package.
Because of the demand for high-density packaging, surface mount leadless packages have become popular. However, denser packaging increases the cross-talk problem. Furthermore, many analog circuits have a high impedance level that makes them particularly sensitive to crosstalk. So, while useful, most surface mount leadless packages provide inadequate electrical and electromagnetic isolation of their components.
Another type of semiconductor package, one that is a hybrid of the surface mount leadless package and a “pin-type” package, is possible. Such a semiconductor package has “pins” that extend from the bottom of the package. Those pins are designed to attach to pads on the surface of a printed circuit board. As electrical connections are not made along the edges of the package, adjacent semiconductor packages can abut, which allows dense packaging. While beneficial, this also increases the cross-talk problem.
Thus, a need still remains for integrated circuit package system that provides electromagnetic isolation of a component mounted therein. More beneficial would be a low cost semiconductor package that enables dense packaging of integrated circuit chips, together with electromagnetic isolation of those chips. In view of the increasing demand for small and highly integrated electronic devices, it is increasingly critical that answers be found to these problems. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to save costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.